Heat exchange apparatus

ABSTRACT

Heat-exchange at least one heat-exchange tube accommodating a centrally disposed, longitudinally extending core having at least three radially extending ribs. The outer ends of the ribs are shaped as wedges whose acute ends extend radially from the center of the core, the ends of the ribs being press-fitted into the tube wall on the inner side thereof to a depth equal to the height of the wedges.

United States Patent Byltov et a1.

[ HEAT EXCHANGE APPARATUS [22] Filed: June 20, 11973 [21} Appl. No.:371,843

[ Mar. 18, 1975 [52] [1.8. CI. 138/38, 165/179 [51] Int. Cl. FlSd l/00[58] Field of Search 165/179, 109 T; 138/38 [56] References Cited UNITEDSTATES PATENTS 2,960,114 11/1960 Hinde 165/179 Primary Examiner-CharlesSukalo [57] ABSTRACT Heat-exchange at least one heat-exchange tubeaccommodating a centrally disposed, longitudinally extending core havingat least three radially extending ribs. The outer ends of the ribs areshaped as wedges whose'acute ends extend radially from the center of thecore, the ends of the ribs being press-fitted into the tube wall on theinner side thereof to a depth equal to the height of the wedges.

2 Claims, 4 Drawing Figures PATENTEDHAR I 81975 sum 1 BF 2 mwLm HEATEXCHANGE APPARATUS The invention relates to the field of refrigeratingmachines, and more particularly to heat-exchange apparatus, such as forrefrigerating machines.

A widely known evaporator of a refrigerating machine comprises a systemof heat-exchange tubes accommodating metallic inserts, each having acentrally disposed, longitudinally extending core provided with aplurality of radially extending ribs integral therewith. The ribs are oftrapezoidal cross section with an enlargement toward the inner side ofthe tube. Each rib terminates in an enlarged shoe which is flat on theside of the outer surface thereof. The centers of the above bases of theshoes are located on a circle of a diameter equal to the inside diameterof the respective tube, and the outer edges of the lateral sides of the"shoes" are located on a circle of a diameter which is greater than theinside diameter of the tube.

When the insert is placed into its tube, the inner surface of the latteris subjected to deformation at the points of contact with the outerlateral sides of the shoe" so that an arc is formed with a radiusgreater than the inside radius of the tube (cf. US. Pat. No. 2,895,506of 1959).

In order to obtain an increased thermal performance, it is necessary toimprove the wetting of the tube surface (vapour separation) and toensure more uniform distribution of the refrigerant between the tubepassages.

For that purpose, in known constructions the ribs are made twisted alonga helical line, and openings are made in the ribs to enable the flow ofthe refrigerant from one passage into another.

Contact heat exchange is improved between the ribs and the tubes byincreasing the area of contact between the ribs and the tube surfaces,and for that purpose the rib bases are made T-shaped.

However, known constructions exhibit the following disadvantages:

Intensity ofheat emission of the ribbed surfaces mainly depends upon theintensity of heat emission of the ribs (since the total surface area ofthe ribs is normally much greater than that of a ribless part of theheat-exhange surface), whereas the helical path of flow results in animprovement of wetting of the inner side of the tube shell (riblesspart). Thus an increase takes place only in regard of the heat emissioncoefficient of the ribless part of the tube, which is of practicallyminor importance from the viewpoint of the total intensity of the heatemission.

The efficiency of the heat transfer from the tube to the core (or viceversa) is rather low.

The use of the Tshaped bases of the core ribs pro-' vides for anincreased contact area between each tube and its ribs, the contact ribtube being, however,

worse.

It is an object of the invention to provide a heatexchange apparatushaving a construction to improve its thermal performance by ensuringmore intensive heat emission of the ribbed cores and by improving thecontact heat exchange between the ribs and the respective tube.

The above object is accomplished by the provision of a heat-exchangeapparatus, comprising at least one heat-exchange tube which accommodatesa centrally disposed, longitudinally extending corc having at leastthree radially extending ribs, the outer ends of the ribs beingpress-fitted into the tube wall on the inner side thereof, wherein theouter ends of the ribs are shaped as wedges according to the invention,the pointed ends of the wedges being directed radially away from thecenter of the core, andthe wedges being press-fitted with their pointedends into the surrounding tube wall to a depth equal to the height ofthe wedges.

This construction permits to substantially increase contact pressurebetween the rib bases and the inner side of the tube, wherebyheat-exchange between the ribs and their tube is improved.

According to the invention the lateral sides of the core ribs may have arough microrelief.

This enables more intensive heat emission of the ribs.

The invention will now be described in detail, with reference to aspecific, preferred embodiment thereof illustrated in the accompanyingdrawings, in which:

FIG- 1 is a longitudinal sectional view of a heat- The apparatusaccording to the invention comprises a cylindrical metallic housing 1(FIGS. 1, 2) having one end tightly closed by means of a spherical endwall 2 welded thereto; an annular flange 3 is welded to the other end ofthe housing and is adapted to support a tube grate 4 and a cover plate5.

The housing 1 accommodates a system consisting of V-shaped heat-exchangetubes 6 having their expanded ends fitted in respective holes of thetube grate 4.

The housing 1 is provided with inlet socket pipes 7, 8 and outlet socketpipes 9, 10 for a coolant and a refrigerant, respectively.

Mounted in each heat-exchange tube 6 is an aluminium insert 11 (FIG. 3),each comprising a centrally disposed, longitudinally extending core 12having a number of radially extending, equally spaced ribs 13.Preferably three ribs are provided in each tube.

The outer ends or bases of the ribs 13 of each insert 11 are shaped aswedges 14, the acute or pointed end of each wedge being directedradially away from the center of the insert 11. The ribs 13 (FIG. 14)are pressfitted with their acute ends into the walls of the respectivetubes 6 on the inner sides thereof to a depth equal to the height of thewedges 14.

In order to improve heat exchange, the lateral sides of the ribs 13 havea rough microrelief 15.

The rough microrelief 15 can be obtained by spraying metal onto thelateral sides of the ribs 13, or by the method of electrochemicaletching.

The microrelief 15 may be of a porous structure, with the void sizebeing commensurable with the diameter of a nucleus of a vapour bubble ofa refrigerant during its boiling on the surface of the heat-exchangetubes 6.

The apparatus functions as follows: Refrigerant is fed into theheat-exchange tubes 6 normally in the form of a vapo liquid mixture.Generally it consists of percent of liquid and 20 percent of vapour.While moving along the tubes 6, the liquid phase of the refrigerant isvaporized.

Having passed the heat-exchange tubes 6, the refrig- I erant iscompletely in the vapour phase.

The provision of the rough microrelief on the lateral sides of the ribs13 enables an increase of the number of the effective vapour formationcenters, thereby making the boiling of the refrigerant more intensive inthe tubes 6.

The improvement of the contact heat exchange is ensured due to the factthat the outer ends or bases of the ribs 13 are shaped as wedges 14which are press-fitted into the wall of the surrounding tube 6 to adepth equal to the entire height of the wedges.

The refrigerant leaving the tubes 6 through the outlet socket pipe 10 issucked into a compressor.

The heat-exchange apparatus according to the invention exhibits thefollowing advantages:

reduced weight and size;

lower manufacturing cost;

lower consumption of refrigerant;

convenient transportation, assembly and operation.

The use of the heat-exchange apparatus according to 4 the inventionmakes it possible to improve the thermal performance by making the heatemission of the ribbed cores more intensive and by improving the contactheat exchange between the ribs and their tube.

What is claimed is:

l. A heat-exchange apparatus comprising: at least one heat-exchangetube; a centrally disposed, longitudinally extending core accommodatedin said tube; at least three radially extending ribs on each core, theouter ends of said ribs being shaped as wedges having pointed endsdirected radially away from the center of said core, and said ribs beingpress-fitted with said ends into the inner wall of said tube to a depthequal to the height of said wedges, thereby raising the contact pressurebetween said outer rib ends and said inner tube wall, with concomitantincreased contact heatexchange characteristics.

2. The apparatus as defined in claim 1, wherein the lateral sides ofsaid ribs have a rough microrelief.

1. A heat-exchange apparatus comprising: at least one heatexchange tube;a centrally disposed, longitudinally extending core accommodated in saidtube; at least three radially extending ribs on each core, the outerends of said ribs being shaped as wedges having pointed ends directedradially away from the center of said core, and said ribs beingpress-fitted with said ends into the inner wall of said tube to a depthequal to the height of said wedges, thereby raising the contact pressurebetween said outer rib ends and said inner tube wall, with concomitantincreased contact heat-exchange characteristics.
 2. The apparatus asdefined in claim 1, wherein the lateral sides of said ribs have a roughmicrorelief.